This invention relates to a muffling device for an outboard propulsion machine and more particularly to an improved silencing device for an outboard motor.
A wide variety of propulsion devices have been proposed for watercraft that are attached to the hull and which provide propulsion for the watercraft. An outboard motor is a typical example of such propulsion devices and includes an internal combustion engine that drives a form of propulsion mechanism such as a propeller or the like for propelling the watercraft. It is the normal practice to enclose the internal combustion engine in a protective cowling to protect it from the elements and also to improve the appearance of the unit. The protective cowling is also intended to serve a silencing function so as to silence noises generated from the engine operation from reaching the occupants of associated watercraft.
However, the internal combustion engine requires air for its operation and therefor the protective cowling is provided with an atmospheric air inlet device to admit air to the engine for combustion. However, these atmospheric air inlet devices thus permit noise emanating from the engine to reach the occupants of the watercraft.
To avoid some of these problems, it has been proposed to form the air inlet opening in the rear portion of the protective cowling and facing away from the watercraft. However, this gives rise to a problem in that water may enter the protective cowling and damage the engine or the engine auxiliaries contained within the protective cowling.
In order to avoid the water damage it has been proposed to provide a duct that extends from the protective cowling into the interior of the watercraft so that the air drawn for the engine operation will be substantially free of water. However, although these devices are effective in reducing the water drawn into the protective cowling, they actually transmit noises from the engine to the occupants of the watercraft. Although the engine itself may be provided with an air silencing device, there also noises generated by the engine and other propulsion components of the outboard motor and vibrations of the protective cowling that which will transmitted and at times amplified by such connecting ducts.
It is, therefore, a principle object of this invention to provide an improved silencing arrangement for a marine propulsion device.
It is a further object of this invention to provide an improved silencing device for a marine propulsion unit which permits effective silencing not only of the inducted air but of the mechanism itself from the occupants of the watercraft.